As a convention used herein, a nerve will be defined as a collection of individual nerve fibers (i.e., axons) of individual nerve cells (neurons) that together form a set of nerve pathways (an integrated set of pathways for signal propagation within the nervous system). Subsets of the individual nerve fibers are each bundled into one of a plurality of fascicles that together form the nerve. Action potentials can occur in the axon portion of individual nerve cells. A series of individual nerve fibers that together form an integrated signal pathway starting at a sensory-receptor nerve ending and extending to the brain will be referred to as a sensory-nerve pathway, a series of individual nerve fibers that together form an integrated signal pathway starting at the brain and extending to a muscle cell will be referred to as a motor-nerve pathway. A sensory-nerve pathway that carries auditory signals will be referred to as an auditory-nerve pathway, and a sensory-nerve pathway that carries signals from the sense-of-balance organs (e.g., the vestibular organs of the inner ear, or perhaps the eyes) will be referred to as a sense-of-balance nerve pathway.
Within each fascicle of a nerve, there will typically be a plurality of sensory-nerve pathways and a plurality of motor-nerve pathways, wherein the number of sensory-nerve pathways will typically be about fifteen times as many as the number of motor-nerve pathways. As well, a series of individual nerve fibers may together form an integrated pathway starting at one of various internal organs and ending in the brain, with then other series of individual nerve fibers together forming an integrated pathway starting at the brain and extending to some internal end organ (such as the digestive tract, the heart, or blood vessels) as part of the autonomic nervous system; and a series of individual nerve fibers may together form an integrated pathway within the brain referred to as a tract. As used herein, a nerve bundle or fascicle refers to a collection of nerve fibers that subserve a like function (e.g., a fascicle may support a plurality of different motor-nerve pathways and thus motor-control signals needed for the muscles for a hand grasp, for example; similarly the same and/or a nearby fascicle may support a plurality of corresponding sensory-nerve pathways and thus sensory signals that provide the brain with feedback for the hand grasp).
Applying an electrical signal across or into a neuron (nerve cell), or a nerve bundle or nerve, is one way to stimulate a nerve action potential (NAP), either in a single neuron (nerve cell), or in a plurality of neurons within a nerve bundle, or within a nerve (the combined signals of NAPs in a nerve bundle or nerve are referred to as a compound nerve action potential (CNAP)). Applying an optical signal (e.g., a short relatively high-power pulse of infrared (IR) laser light, for example at a signal wavelength about 1.9 microns) is another way to stimulate a NAP.
U.S. patent application Ser. No. 12/018,185 filed Jan. 22, 2008, titled “Hybrid Optical-Electrical Probes” by Mark P. Bendett and James S. Webb, which is incorporated herein by reference in its entirety (and which issued as U.S. Pat. No. 7,883,536 on Feb. 8, 2011), describes an optical-signal vestibular-nerve stimulation device and method that provides different nerve stimulation signals to a plurality of different vestibular nerves, including at least some of the three semicircular canal nerves and the two otolith organ nerves. In some embodiments described in that patent application, balance conditions of the person are sensed by the implanted device, and based on the sensed balance conditions, varying infrared (IR) nerve-stimulation signals are sent to a plurality of the different vestibular nerves. Also described is a method that includes obtaining light from an optical source; transmitting the light through an optical fiber between a tissue of an animal and an optical transducer, and detecting electrical signals using conductors attached to the optical fiber. The application also describes an apparatus that includes an optical source, an optical transmission medium operatively coupled to the optical source and configured to transmit light from the optical source to respective nerves of each of one or more organs of an animal, an electrical amplifier, and an electrical transmission medium integral with the optical transmission medium and operatively coupled to the electrical amplifier, wherein the electrical transmission medium is configured to transmit an electrical signal from the respective nerves to the electrical amplifier.
One way to treat deafness in a person is to implant a cochlear-stimulation device (frequently called a cochlear implant) that senses sound in the environment (e.g., using a microphone) and then generates a combination of different electrical signals in different locations in the person's cochlear inner-ear structure. Because it is difficult to confine the electric field of each one of a large number of separate electrical signals, each intended for a particular one of a large number of separate nerves, e.g., among those nerves that extend in the bundle from the cochlea into the brain (it is possible to generate CNAP responses in perhaps only sixteen different nerve pathways (channels)), this conventional approach can provide only a crude representation of normal hearing.
U.S. Pat. No. 6,921,413 issued Jul. 24, 2005 to Mahadevan-Jansen et al., titled “Methods and devices for optical stimulation of neural tissues,” and U.S. patent application Ser. No. 11/257,793 filed Oct. 24, 2005 by Webb et al., titled “Apparatus and method for Optical Stimulation of Nerves and Other Animal Tissue,” are each incorporated herein by reference in their entirety. Both of these describe optical stimulation of nerves in general.
U.S. Patent Application Publication No. US 2006-0161227, of Walsh et al., titled “Apparatus and Methods for Optical Stimulation of the Auditory Nerve,” is incorporated herein by reference in its entirety. This application describes a cochlear implant placed in a cochlea of a living subject for stimulating the auditory system of the living subject, where the auditory system comprises auditory neurons. In one embodiment, the cochlear implant includes a plurality of light sources {Li}, placeable distal to the cochlea, each light source being operable independently and adapted for generating an optical energy, Ei, wherein i=1, . . . , N, and N is the number of the light sources, and delivering means placeable in the cochlea and optically coupled to the plurality of light sources, {Li}, such that in operation, the optical energies {Ei} generated by the plurality of light sources {Li} are delivered to target sites, {Gi}, of auditory neurons, respectively, wherein the target sites G1 and GN of auditory neurons are substantially proximate to the apical end and the basal end of the cochlea, respectively.
U.S. Patent Application Publication No. US 2005 0004627 titled “Auditory midbrain implant” filed by Peter Gibson et al. on Aug. 26, 2004 is incorporated herein by reference. This application describes an electrode array that is implantable within the inferior colliculus of the midbrain and/or other appropriate regions of the brain of an implantee and adapted to provide electrical stimulation thereto. The electrode array an elongate member having a plurality of electrodes mounted thereon in a longitudinal array. A delivery cannula for delivering the electrode array comprised of two half-pipes is also described.
There is a need for efficacious apparatus and methods for optically, or optically and electrically, stimulating auditory nerve and/or brain tissue in a living animal in order to generate a nerve action potential (NAP) in one neuron (nerve cell), or in multiple neurons within a nerve bundle or nerve (where the combined individual NAPs form a compound nerve action potential, or CNAP), or similar physiological response in the animal. Optical or electrical-and-optical stimulation of neurons can provide more precision in terms of stimulating a particular nerve pathway than is possible using only electrical stimulation.